Can I use your Rail Runner tool to shape the rail bands?
The "fred tool" part of the rail runner is for the bottom tuck only. The bottom tuck is normally anywhere from a 3/8" - 3/4" radius (depending on your preference) and the rail bands are cut in the the rail runner.
The deck rail bands are much bigger and not a "radius" but an arc or curve. The rail bands are created with a power planer or G-rasp tool and the sharp corners of the rail bands are cut down by rail screen (you should be using a more aggressive screen like the sand shark screen to shape the rails down... they'll come out round and less angular or boxy)
Think of the rail bands as facets of a diamond. Flat surfaces intersecting at points. There is a curve hiding in there that is exposed when the corners are screened off.
More info and dimensions for rail band shaping in our Surfboard Building Guide